The present invention generally relates to apparatus and methods for continuously, automatically and dynamically regulating the flow of manufactured articles in an automated multi-step manufacturing setting. More particularly, it relates to a new and improved automated workload balancer for use in automated manufacturing lines having an improved transfer and storage arrangement and improved article management features adapted to provide article handling rates of above about 5,000 articles per minute, and preferably between about 7,500 about 10,000 articles per minute.
An automated workload regulator apparatus for use in automated manufacturing operations is known from U.S. Pat. 4,808,057 issued Feb. 28, 1989 and U.S. Pat. No. 4,983,095 which issued Jan. 8, 1991, both of which are assigned to the same assignee as the present invention. In accordance with the apparatus and method defined in these patents, the preferred articles are can lids or ends which are stamped from a roll or sheet of metal stock at a first stamping operation and work station. The stamped can ends are transferred to successive downstream workstations where a number of subsequent manufacturing operations are or may be performed including: a shaping operation whereat the curled edge portion is imparted to each can end which is subsequently used in securing the can end to a can body; liner operations, wherein various coating compounds are applied to the inside surface of the can end preparatory to sealing of the can end to a can body; drying operations, to dry or cure the coatings applied in the liner operations; conversion press operations, wherein the easy open score lines and pop-top tab rings are stamped and affixed to each lid, respectively; packaging operations, wherein a predetermined number of can ends are packaged in a tubular paper sleeve wrapper in trays or boxes, and finally, palletizing and shrink or stretch wrapping operations, wherein sticks or packaged sleeves of can ends are stacked onto a pallet and wrapped in heat-shrink or stretch type plastic wrap for safe-keeping in temporary storage.
The balancer apparatus is positioned between two adjacent work stations to promote maximum, through-put or output from the overall manufacturing operation by permitting uninterrupted operation of at least one of the workstations at its desired operating rate even though the other workstation is experiencing an intermittent or variable operating rate.
The apparatus described in the aforementioned patents includes a transfer station having an associated inbound staging area, an outbound staging area and a storage area. As shown in the patent drawings, the inbound staging area and the outbound staging area each comprise a plurality of adjacent parallel lanes and preferably the inbound and outbound staging areas are disposed in adjacent, side by side relation in a common horizontal plane extending through the transfer station. The storage area is defined by a horizontal conveyor extending parallel to the staging areas but spaced vertically below the staging areas. A gap or separation is provided between the inbound and outbound lanes at the transfer station. The horizontal conveyor is designed to receive and index a storage tray having a plurality of parallel troughs or receptacle portions, each for receiving a stick of can ends, in either of two horizontal directions, e.g. into or away from the transfer station.
A transfer head having gripping and releasing means for grabbing a stick of can ends is positioned at the transfer station and is capable of a limited range of movement along the two axes in the transfer station. The transfer head can move a stick of ends from an inbound lane at the inbound staging area to an outbound lane at the outbound staging area or it can move the stick from the inbound lane downwardly to a centrally positioned empty trough in the storage tray positioned at the central location in the transfer station. In addition, the transfer head may grip a stick of can ends from a trough in the storage tray and deposit it in an outbound lane.
The balancer apparatus described in these patents further includes an empty container magazine and a full container magazine located at the opposed ends of the horizontal conveyor, respectively. Each magazine includes elevator means for upstacking or downstacking a given number of storage trays and for cooperatively loading them one at a time from magazine storage onto the horizontal conveyor for indexing through the transfer station.
In accordance with the apparatus and its mode of operation, a number of sensors and a controller module determine the cumulative inbound rate of can ends or rather the sticks of can ends being deposited in the lanes at the inbound staging area. Moreover, the controller also determines a cumulative outbound rate which is the rate at which sticks of ends are being withdrawn from the outbound lanes of the outbound staging area. The transfer head moves one group or stick of ends at a time and removes sticks from the inbound staging area at a first pick up rate equal to the cumulative inbound rate. The transfer head also places sticks of can ends in the outbound staging area at a placement rate equal to the cumulative outbound rate. The controller and apparatus balances the pick up rate with the placement rate by directing the transfer head to additionally transfer a sufficient number of groups to and/or from storage so that a desired regulated flow is achieved or maintained by the overall operation.
In accordance with this apparatus, the storage tray conveyor and respective magazines permit continuous regulated flow to occur even when one of the work stations is experiencing interrupted operation for any time period. In a start-up sequence, for example, a supply of empty storage trays equal to a maximum number of trays that can be handled by either of the magazines is loaded into the empty tray magazine. The transfer head is programmed to load each stick of can ends arriving at the inbound staging area into a receptacle portion or trough in a storage tray. Accordingly, a first empty tray ,s deployed from a stack of empty trays in the empty tray magazine onto the horizontal crossfeed conveyor. The tray is moved to the transfer station and then indexed therethrough as the transfer head places sticks of can ends one stick at a time into a receptacle trough portion. This series of steps is repeated until all of the receptacle portions of the storage tray are filled. Thereafter, the filled tray is moved by the conveyor to the filled container magazine.
At the filled container magazine, a lift engages the bottom of the filled storage tray and raises it to an extended position. Thereafter, side mounted holder fingers are actuated to an inwardly extended position wherein the fingers are located under the edges of the raised storage tray. The holder fingers may also be actuated to a retracted position out of the path of the lift area. Once the trays have been shifted and the holder fingers have been moved to their inwardly extended position under the stack of filled storage trays, the lift mechanism is lowered until the lowermost tray rests o the extended holder finger supports in a raised and stored position within the filled container magazine spaced above the crossfeed conveyor. This start-up sequence is repeated until a desired number of trays are filled which are loaded into the filled tray magazine.
In accordance with the apparatus and method described in this patent, a fixed number of storage trays may be shuttled back and forth between the filled container magazine and the empty container magazine, as required in operation. The apparatus described in U.S. Pat. No. 4,808,057 was designed for use in can end manufacturing systems having operating rates of between about 2,000 to about 5,400 or more ends per minute. Typically, ends are stamped in a stamping press and are then passed through curl wheels to impart the curled peripheral lip portion. Good operating rates with these systems are generally from about 2,500 to 4,000 ends per minute.
More recently, advances have been made in the stamping and forming operations. More particularly, new and improved end die presses have been developed which stamp the can ends from rolled and sheet stock and simultaneously provide the peripheral curled lip portion in a single or dual stroke of the stamping die. These newer die curl presses are running at 250 strokes per minute and are expected to be able to perform at rates of 300 to 350 strokes per minute in the future. In this modern manufacturing context, a typical die may produce as many as 28 can ends for each stroke and at an operating rate of 300 strokes per minute, the modern stamping operations are expected to be producing at least about 8,400 can ends per minute.
This four-fold increase in production rate must be matched or accommodated by the operating rates and capacities of either the related workstations or the automated workload balancers required between workstations in the production line. Pressure to improve the operating rates of each successive workstation has also been prompted by this improvement in stamping operations. The balancer described in the above-mentioned patent and patent application has a practical upper limit of about, an operating rate of about 5,400 ends per minute, which rate is insufficient for more modern manufacturing operations.
More recently an improved, high capacity workload balancer apparatus has been introduced which is described in copending commonly assigning U.S. application Ser. No. 787,730, filed Nov. 4, 1991, which is a Continuation of U.S. application Ser. No. 550,476 filed Jul. 10, 1990. The new and improved balancer apparatus described in this application achieves increased transfer rates by a modification of the transfer mechanism and its movements. Instead of having a storage tray being indexed under a central location of a transfer station to present one article stick receiving trough at a time to the transfer head, a storage tray is positioned in parallel side by side relation to the inbound lanes, the outbound lanes, or both, within the operating range of motion of the transfer head. In accordance with this modification, the transfer head can move overhead to any designated lane and to any designated trough positioned at the transfer station. In addition to increasing the rate of transfer with the more flexible movement capability of the transfer head, the balancer described in this application includes an increased capacity storage facility. More particularly, at least one elevator module is provided having a shaft extending through the transfer station. A pallet of trays may be advanced on demand to the elevator shaft and one tray at a time may be presented through the transfer station. When an entire pallet of trays is filled up or emptied, the pallet is advanced out of the elevator shaft to a pick up area. A fork lift operator may remove a pallet of filled storage trays out of the line at this point if necessary. In accordance with this aspect of the improved balancer the pallet/elevator arrangement manages groups of groups trays for increased storage capacity whereas the earlier conveyor/magazine storage arrangement generally managed a single group of trays at a time. The higher capacity balancer equipped with a dual transfer head and dual elevator system is rated at speeds above about 6,000 to about 8,000 articles per minute or more. The pallet and elevator systems however are relatively expensive and undesirably increase the cost of the overall balancer apparatus.
Accordingly to further improve upon the prior art automated balancers, it is an object of the present invention to provide a new and improved automated workload balancer apparatus capable of accommodating operating rates above about 5,000 articles per minute and preferably between about 7,500 to about 10,000 articles per minute at a reduced overall cost.
It is another object of the present invention to provide a new and improved automated workload balancer having an improved transfer station and transfer mechanism including an increased number of lanes and a new and improved transfer head assembly having an expanded range of reciprocal movements within the larger transfer station.
It is a further object of the present invention to provide a new and improved high speed and high capacity balancer apparatus capable of maintaining the articles to be moved in a desired transfer orientation and configuration.